Refrigeration system and flexible coupling for concentric shafts



Nov. 17, 1964 K. A. OBER 3,157,129

SYSTEM A REFRIGERATION FLEXIBLE COUPLING FOR CONCENT SHAFTS Filed June 15, 1962 2 Sheets-Sheet 1 3 INVENTOR. Kenneth A. Ober A TTORNEYS Nov. 17, 1964 B R 3,157,129

K. A. O E REFRIGERATION SYSTEM AND FLEXIBLE COUPLING FOR CONCENTRIC SHAFT-S Filed June 15. 1962 2 Sheets-Sheet 2 IN VENTOR.

Kenneth A. Ober BY United States Patent 3,157,129 REFRIGERATIGN SYSTEM AND FLEXIBLE CQU- FLING FGR CUNCENTRIC SHAFTS Kenneth A. (fiber, North Coventry, Conn, assignor to Dunharn-Eush, Inc, West Hartford, Conn, a corporation of Connecticut Filed June 15, 1962, Ser. No. 202,754 7 Claims. ((11. 103-37) This invention relates to refrigeration systems and the like, and more in particular to improving the operating characteristics of such systems. In its broader aspects, this invention relates to improved mechanical driving means between an electric motor and a driven refrigerant compressor or other pump or similar device, and to the combination of the electric motor with the driven device.

In refrigeration systems having compressors of the open type it is the accepted practice to drive the compressor with an electric motor having its shaft in alignment with the compressor shaft, that is, in end-to-end relationship. The shafts are connected by rigid means so that the rotor of the motor and the shafts of the motor and compressor constitute a relatively rigid driving unit projecting from the stator of the motor into the compressor. Such driving arrangements are satisfactory where the shafts of the motor and the compressor are in exact alignment. However, the motor shaft is mounted in bearings on the motor frame and the compressor shaft is mounted in bearings on the compressor frame and then both frames are bolted to a common base, and the tolerances of manufacturing and the conditions during distribution, installation and use cause the axes of the two shafts to be slightly out of alignment. Such misalignment may also result from bearing wear or from a slight shift of the motor with respect to the compressor. The two axes may be at a slight angle to each other, i.e., not parallel, or one axis may be above, or below, or at the side of the other, even though they are exactly parallel. It is diflicult to provide adequate tests to prevent misalignment even during assembly of motor compressor units, and it is even more difficult to provide such tests in the field, that is, after the refrigeration system is installed for operation. Also, the cost of such tests is high relative to the value of the equipment.

It is an object of this invention to overcome the difficulties referred to above. It is a further object to provide an improved unit comprising a driving motor and a driven device of the above character with there being a flexible mechanical connection therebetween. It is a further object to provide improved driving mechanisms. It is a further object to provide improved refrigeration systems. It is a still further object to provide for the above with constructions which are adaptable to various conditions or use and which are simple and compact. These and other objects will be in part obvious and in part pointed out below.

In the drawing wherein one embodiment is shown:

FIGURE 1 is a refrigeration system incorporating the present invention;

FIGURE 2 is an enlarged perspective view of the drive mechanism of FIGURE 1 which connects the compressor of the refrigeration system to the electric motor which drives it;

FIGURE 3 is a sectional view of the line 33 of FIG- URE 2;

FIGURE 4 is a sectional view on the line 4-4 of FIG- URE 3;

FIGURE 5 is a fragmentary view on the line S5 of FIGURE 3;

FIGURE 6 is a front elevation of operating unit constituting one embodiment of the invention; and,

3,1511% Patented Nov. 17, 1964 FIGURE 7 is an enlarged sectional view of the flexible coupling of FIGURE 6.

Referring to FIGURE 1 of the drawing, a self-contained liquid chiller 2 has a rigid frame construction upon which is rigidly mounted a refrigeration system having a compressor 4 driven by an electric motor 6 through a flexible coupling 8. The refrigeration system also includes a condenser-receiver assembly 12 an evaporator assembly 14 where liquid is cooled, and standard control and safety components. During assembly, the motor shaft 16 and compressor shaft 14 are positioned in endto-end axial alignment (see FIGURE 4) and are interconnected by the fiexible coupling 8.

Coupling 8 is formed by a coupling member 20 mounted upon and keyed to shaft 16, a coupling member 22 mounted upon and keyed to shaft 18, and a set of flexible straps which interconnect the two coupling members and which are described below. Coupling member 20 has a hub 24 and a rim 26, and projecting parallel to the axis of the coupling member are three brackets 28 (see also FIGURE 3) which are equally spaced arcuately so as to be positioned from each other. Coupling member 22 has a hub 30 and similar brackets 32 which are equally spaced so as to be 120 apart. Brackets 28 and 32 are at the same radius and brackets 28 are positioned respectively equidistant between brackets 32. In FIGURE 3 the direction of rotation is clockwise, and each bracket 28 is 60 from two brackets 32, one trailing and the other leading. Each bracket 28 is connected to the bracket 32 which trails it by a flexible nylon strap 34 and is connected to the bracket 32 which leads it by a nylon strap 36. Straps 36 are at a lesser radius than straps 34, and each strap end is folded over and fused to itself to form a double thickness connection portion. These folded strap ends at each bracket are clamped to the bracket by a pair of lag bolts 38 and a rectangular metal clamping plate 40, the end of the strap 36 being against the bracket and the clamping plate 40 engaging the strap 34. Each of straps 34 has on its inner surface a weight 42 (see also FIGURE 5) which is a quantity of lead pellets positioned in a pocket formed by a sheet of nylon stitched or fused to the strap surface. These three weights are equal and the amount of weight is selected depending upon the characteristics of the particular installation and the conditions of operation. Each of the clamping plates 40 has a pair of parallel ridges 41 which produce spaced clamping zones within which the ends of the straps are tightly held. The entire construction is dynamically balanced from both the driving and driven sides.

When motor 6 is operated, coupling member 20 turns and each of the brackets 28 exerts a pulling force through its strap 34 to its trailing bracket 32. This drives coupling member 22 and with it shaft 18 and the operating parts of the compressor. As the motor and compressor approach full speed, the three weights 42 tend to move radially outwardly and this tends to reduce the effective length of each of the straps 34. This causes the brackets 28 to advance somewhat with respect to brackets 32, that is, the angle between each bracket 28 and the bracket 32 which trails it may be reduced slightly during start-up so as to be less than 60, and the angle between each bracket 28 and the bracket 32 which leads it becomes more than 60. At full speed these angles would be 60". With this operating condition straps 34 are bulged outwardly, whereas straps 36 are drawn toward a straight or less arcuate condition.

When the axes of the two shafts are in exact alignment and there are no fluctuations in the operating conditions, the straps 34 and 36 maintain fixed contours and the relative positions of brackets 28 and 32 remain unchanged. However, if the axes of the two shafts 16 and 13 are not in exact alignment, brackets 28- and 32 do not maintain their exact relative positions. That is, during each rotation, there is relative movement between each bracket and the next adjacent brackets, but the relative movement is taken up by slight flexing of the connecting straps 34 and 3d. Also weights 42 move radially in and out slightly and cause each strap 3-4 to maintain a constant pull upon its bracket 32. Also, the weights combine with the straps 34- to insure that there is a constant load upon the brackets 28. Therefore, a floating drive is provided wherein each bracket 28 exerts a turning force upon its trailing arm 32 through its slightly bulged strap 34, and this driving effect is unchanged even though the axes of rotation of the two coupling members are not in exact alignment. The weights provide a centrifugal force effect which shapes the straps arcuately. This causes the forces to be substantially tangential rather than chordal and reduces the stresses on the straps for a given torque.

Flexible coupling 8 also provides a very efficient and dependable driving connection between motor 6 and compressor 4 throughout wide variations in the operating conditions. When the electric power to motor 6 is turned off so that the motor decelerates, the restraining straps 36 become effective between each bracket 28 and the bracket 32 which leads it. This insures that the rotating parts of the compressor will decelerate and stops simultaneously with the rotor of the motor. The reduced speed causes a gradual reduction in the effects of Weights 42 so that all of the straps 34 and 36 return to the arcuate condition of FIGURE 3.

The flexible coupling 8 also has special advantages in the particular combination with an electric motor and the compressor of a refrigeration system. With such a system, the load on the motor varies quite widely and the variations may be very sudden and extreme. With a refrigeration system which has a rigid connection between the motor shaft and the compressor shaft, fluctuations in the load are transmitted directly to the motor, while the constant driving force of the motor is transmitted directly to the rotating parts of the compressor. The load fluctuations may be cyclic or irregular and may be sudden or gradual. They may cause serious problems or malfunctioning, excessive noise or vibration, or excessive wear or damage to parts. Hence, with prior systems the fluctuating load conditions have produced serious problems.

With the present invention the flexible coupling 8 tends to absorb fluctuations in the load with only slight flexing of the straps 34 and 36. This is particularly apparent when the fluctuations cause sudden shock impulses which are absorbed by coupling 8, but which would be troublesome with prior systems. The flexible coupling 8 provides a cushioning effect between the rigid driving force of the motor and the somewhat rigid but fluctuating load of the compressor. Hence, the refrigeration system of the present invention has a motor-compressor assembly which operates to improve the over-all operation of the refrigeration system. The compressor is driven in a satisfactory manner at all times. That is, when operating conditions cause load fluctuations which would normally cause difficulties, the flexible coupling produces sufficient corrective changes in the driving effect to maintain constant operation.

In the embodiment of FTGURES 6 and 7, a pump 64 is driven by an electric motor 66 through a flexible coupling 68. The motor and pump are rigidly mounted upon a base and the pump has a bearing assembly '70 from which the driven shaft 68 projects (see FIGURE 7). Shaft 68' is in end-to-end alignment with shaft 66 of motor 66. Mounted upon shaft to is a coupling member 70 which has a hub 74 keyed to the shaft and clamped thereto by a set screw. Integral with hub 74 is a shell-like flange structure formed by a disc portion and a peripheral collar portion. A similar coupling member '72 is keyed to shaft 68 and has a similar shell-like flange structure. These flange structures form a protective shell casing.

Each of coupling members 70 and 72 has three equally spaced brackets 70 and 72', respectively, corresponding to brackets 28 and 32 of FIGURES 1-4 (see also FIG- URE 8). Driving straps 84 with weights 92 and restraining straps 36 correspond respectively to straps 34 and 36 of FIGURES 14. The strap ends are clamped to the respective brackets with metal spacers 85 and with clamping set screws. The operation of the embodiment of FIG- URES 6, 7 and 8 is similar to the motor-compressor operation of the embodiment of FIGURES 1 to 5. Pump 64 is driven in a dependable manner under widely varying conditions of use.

As many possible embodiments may be made of the mechanical features of the above invention and as the art herein described might be varied in various parts, all without departing from the scope of the invention, it is to be understood that all matter hereinabove set forth, or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. In a refrigeration system having an evaporator and a condenser and circuit means connected therebetween and a motor compressor unit for withdrawing refrigerant from the evaporator and delivering it at elevated pressure to the condenser, said motor compressor unit being of the type having an electric motor and a compressor with shafts upon substantially the same axis and mounted in end-to-end relationship, a flexible coupling connecting the adjacent ends of said shafts and comprising, a pair of coupling members fixed respectively to the adjacent ends of said shafts and each having a plurality of brackets positioned at a predetermined radius from said axis with said brackets being equally spaced from each other, each of said brackets upon each coupling member being positioned arcuately between two of said brackets on the other coupling member, and a plurality of straps corresponding in number to the number of said brackets and serially positioned in circumferential relationship around said brackets with each strap having one end connected to a bracket on thecoupling member fixed to the motor shaft and its other end attached to a bracket on the coupling member fixed to the compressor shaft whereby one-half of said straps cons 'tute driving straps for transmitting driving forces from the motor to the compressor and the other straps constitute restraining straps.

2. In apparatus of the character described, the combination of, a fluid pump having a drive shaft, an electric motor having a driving shaft, said shafts being mounted on substantially the same axis and in end-to-end relationship and coupling means interconnecting the adjacent ends of said shafts comprising a pair of coupling members mounted upon and keyed to the respective shaft ends whereby one coupling member constitutes a driving coupling member fixed to said driving shaft and the other constitutes a driven coupling member mounted upon and keyed to said driven shaft, a plurality of driving straps each fixed at one end to said driving coupling member and at its other end to said driven coupling member, said driving straps being symmetrically positioned with respect to said axis both radially and arcuately whereby said driving straps will cooperate to exert separate and equally spaced driving forces between said driving coupling member and said driven coupling member, each of said driving straps including weight means at its center which causes the strap to tend to bulge during the operation of said compressor by said motor.

3. Apparatus as described in claim 2 wherein said straps are nylon having pockets at their centers and wherein said weight means are pieces of metal positioned within said pockets.

4. Apparatus as descrbied in claim 3 wherein said fluid pump is a compressor for a refrigeration system.

5. A flexible coupling of the character described comprising, a driving coupling member having a hub portion which is adapted to be rigidly mounted upon a driving shaft and a plurality of driving brackets projecting parallel to the axis of said shaft and positioned symmetrically at the same radius therefrom, a driven coupling member having a hub portion which is adapted to be rigidly mounted upon a driven shaft in axial end-to-end alignment With said driving shaft and a plurality of driven brackets corresponding in number to said driving brackets and projecting parallel to said axis and positioned syrnetrically at the same radius therefrom, said driven brackets overlapping axially with said driving brackets and being symmetrically positioned arcuately whereby each driven bracket is positioned at a trailing angle with respect to an adjacent driving bracket, a plurality of driving straps corresponding in number with said driving bra kets with each driving strap being connected at one end to the respective driving bracket and at the other end to the next adjacent trailing driven bracket whereby the predetermined direction of rotation of said driving coupling member transmits its rotation through said driving straps to said driven coupling member, each of said coupling members having an integral shell construction formed by an annular portion projecting outwardly from the hub portion and a cylindrical portion at the periphery of the annular portion and surrounding a portion of the brackets.

6. A flexible coupling as described in claim 5 which includes a plurality of restraining straps corresponding in number with said driving straps With each restraining strap being connected at one end to the respective driven bracket and at the other end to the next adjacent trailing driving bracket, said restraining straps being at a lesser radius than said driving straps.

7. A flexible coupling as described in claim 6 which includes a plurality of weights corresponding in number to said drivnig straps with each Weight being mounted upon the respective driving strap.

References Cited in the file of this patent UNITED STATES PATENTS 322,866 Tabor July 21, 1885 1,096,162 Fawcus May 12, 1914 1,934,l Van Deventer Nov. 7, 1933 2,626,238 Loane et al Dec. 31, 1935 2,344,706 Kucher Mar. 21, 1944 2,778,663 Provost Jan. 22, 1957 FOREIGN PATENTS 321,999 Great Britain Nov. 28, 1929 

1. IN A REFRIGERATION SYSTEM HAVING AN EVAPORATOR AND A CONDENSER AND CIRCUIT MEANS CONNECTED THEREBETWEEN AND A MOTOR COMPRESSOR UNIT FOR WITHDRAWING REFRIGERANT FROM THE EVAPORATOR AND DELIVERING IT AT ELEVATED PRESSURE TO THE CONDENSER, SAID MOTOR COMPRESSOR UNIT BEING OF THE TYPE HAVING AN ELECTRIC MOTOR AND A COMPRESSOR WITH SHAFTS UPON SUBSTANTIALLY THE SAME AXIS AND MOUNTED IN END-TO-END RELATIONSHIP, A FLEXIBLE COUPLING CONNECTING THE ADJACENT ENDS OF SAID SHAFTS AND COMPRISING, A PAIR OF COUPLING MEMBERS FIXED RESPECTIVELY TO THE ADJACENT ENDS OF SAID SHAFTS AND EACH HAVING A PLURALITY OF BRACKETS POSITIONED AT A PREDETERMINED RADIUS FROM SAID AXIS WITH SAID BRACKETS BEING EQUALLY SPACED FROM EACH OTHER, EACH OF SAID BRACKETS UPON EACH COUPLING MEMBER BEING POSITIONED ARCUATELY BETWEEN TWO OF SAID BRACKETS ON THE OTHER COUPLING MEMBER, AND A PLURALITY OF STRAPS CORRESPONDING IN NUMBER TO THE NUMBER OF SAID BRACKETS AND SERIALLY POSITIONED IN CIRCUMFERENTIAL RELATIONSHIP AROUND SAID BRACKETS WITH EACH STRAP HAVING ONE END CONNECTED TO A BRACKET ON THE COUPLING MEMBER FIXED TO THE MOTOR SHAFT AND ITS OTHER END ATTACHED TO A BRACKET ON THE COUPLING MEMBER FIXED TO THE COMPRESSOR SHAFT WHEREBY ONE-HALF OF SAID STRAPS CONSTITUTE DRIVING STRAPS FOR TRANSMITTING DRIVING FORCES FROM THE MOTOR TO THE COMPRESSOR AND THE OTHER STRAPS CONSTITUTE RESTAINING STRAPS. 